Many types of industrial equipment, such as machine tools, production presses, rotary air compressors and others, generate objectionable levels of dynamic shock, vibration forces and noise during operation. Other types of industrial equipment are adversely affected by shock and vibration which may be transmitted to them through the factory floors or foundations on which they are mounted. Some such equipment may be unstable because of cyclical thrust forces or changes in center of gravity which occur during operation. Additionally, most mechanically operable industrial equipment is susceptible to misalignment by reason of load or dynamic forces exerted upon the supporting framework, and when a machine is not properly aligned, the bearings or guides are likely to develop excessive friction, waste energy and wear out faster.
For many years, factory installation and maintenance personnel have attempted to alleviate these problems by using resilient mounts to cushion vibration or shock and by painstakingly shimming up the equipment at various support points so as to improve the alignment. Such equipment is sometimes bolted to the factory floor or to a massive foundation to hold it securely in place. The inadequacy of these procedures for optimizing equipment performance has become increasingly apparent to those who have made a serious study of the operational dynamics of industrial equipment. Moreover, as production equipment continues to become more sophisticated and costly, it is increasingly apparent that a more scientific approach is needed, not only to the initial installation of such equipment, but also to the subsequent monitoring of its performance. For example, when changes are made in the moving parts attached to the machine, or when operating speeds are changed, these may affect the dynamic or load forces exerted by the equipment. Unless those forces can be monitored during operation, there is no reliable way of ascertaining when potentially hazardous dynamic forces are developing or determining when the maximum safe operating speed has been reached. As will be understood, a machine that is out of balance by an insignificant amount at a particular operating speed may become dangerously unbalanced if the operating speed is increased, or one set of dies is replaced with a heavier set. Conversely, a reduction in the weight of certain moving parts might permit an increase in the safe operating speed, provided the operator had some way of measuring quantitatively the changes in operating dynamics under varying operating conditions.
Recent developments in legislation relating to occupational safety and health and to environmental protection have made it increasingly important for plant managements to be able to measure, analyze and control the vibration, shock and noise generated by operating equipment. Such studies of equipment operation are usually made with whatever measuring instruments may be available for making various tests. In some cases sensors, such as accelerometers, are attached to the exterior surface of the machine. In others, sensors such as load cells are interposed between the machine mounting foot and the foundation. Occasionally, resistance strain gauges are applied directly to machine elements such as support legs to determine forces in such elements. The introduction of such extraneous measuring devices into a unit of equipment under observation may affect the validity of the results. As an example, the interposition of extraneous load cells into the machine support system may have some effect on the operating characteristics they are intended to measure.
It was the need for noise suppression, vibration control and precision adjustability to compensate for floor irregularities and misalignment which led to the development of adjustable vibration isolators of the type disclosed in my U.S. Pat. No. 3,332,647, granted July 25, 1967. Such isolators have been widely adopted because of the contribution they make to quieter, more efficient operation of industrial equipment.
Despite the contribution which adjustable vibration isolators have made to quieter, safer and more efficient plant operation, their full potential has not been realized because of the lack of practical means for continuous monitoring of the operating characteristics of the equipment mounted thereon and of the dynamic forces generated thereby, because of the inconvenience of having to attach sensors to existing equipment installations and because the data obtained therefrom is likely to be misleading due to the influence of extrinsic factors.